Grinding wheel guard and safety shutter for abrading machines



E. L. KALLANDER GRINDING WHEEL GUARD AND SAFETY SHUTTER FOR ABRADING MACHINES Flled Jan 5, 1967 July l, l969 ATTORNEY United States Patent O 3,452,489 GRINDING WHEEL GUARD AND SAFETY SHUTIER FOR ABRADING MACHINES Ernest L. Kallander, Southboro, Mass., assignor to Norton Company, Worcester, Mass., a corporation of Massachusetts Filed Jan. 3, 1967, Ser. No. 606,800 Int. Cl. B24b 55/04 U.S. Cl. 51-269 5 Claims ABSTRACT F THE DISCLOSURE On a guard for an abrading or grinding machine having a grinding wheel rotatably mounted thereon, comprising a housing having spaced generally parallel side portions on opposite sides of the grinding wheel and a peripheral portion interconnecting the side portions and enveloping at least half the periphery of the grinding wheel, said peripheral portion including an adjustable hood pivotally connected to the relatively xed section of said peripheral portion and clamped in fixed relation to the side portions, the improvements including:

(a) A safety shutter disposed within the adjustable hood having a turned out upper rear lip portion, a turned in lower forward lip portion, and spaced parallel side portions respectively parallel to the side portions of the adjustable hood;

(b) A four bar linkage pivoted on the inside of the side portions of the adjustable hood and the outside of the side portions of the safety shutter;

(c) A turned in lip portion on the lower forward edge of the adjustable hood for engagement with the turned out lip portion on the upper rear edge of the safety shutter; and

(d) Shear pins releasably interconnecting the side portions of the safety shutter and the side portions of the adjustable hood.

Cross-reference to a related application Reference is made to the copending application Ser. No 606,799 of Backer and Dahlin entitled Grinding Wheel Guard for Abrading Machines the disclosure of which is incorporated herein, iiled Ian. 3, 1967.

Background of the invention The iield of the invention is abrading machines and is particularly concerned with frames and mounts therefor. The grinding Wheel guard of the present invention is included in this eld of invention.

Grinding Wheels up to several feet in diameter and several inches thick are used on various types of abrading or grinding machines for removing stock from and finishing workpieces of metal and other materials, and their most efiicient operation may require rotation of these grinding wheels at speeds suicient to produce speeds as high as 16,000 surface feet per minute at the circumference of such grinding wheels. Since a grinding wheel rotating at 'the required speed develops a substantial quantity of kinetic energy which may be released with fragments of the grinding wheel if it is broken while it is rotating at its operating speed, it has long been customary to enclose such grinding wheels in xed guards commonly including spaced side portions on opposite sides of the grinding wheel and a peripheral portion concentric of the grinding wheel and enclosing its entire periphery except for an area immediately adjacent to the line of contact with a workpiece to be ground, in order to provide as much protection as possible for the operator usually stationed in front of the grinding machine in line with the grinding wheel. However, it has been noted that a grinding wheel guard with a peripheral portion concentric of the grinding wheel may serve as a conduit to direct Wheel fragments through the opening in the guard in the -direction of the operator. See U.S. Patent No. 626,544 of Konrad.

The copending application referred to above describes and claims a modified wheel guard including a non-concentric peripheral portion cut away over almost half the circumference of a grinding wheel to avoid this channeling effect, and thereby effective, in the event of a Wheel failure, to sharply reduce the percentage of the weight of the grinding wheel discharged from the guard in the direction of the station occupied by the grinding machine operator. The hazardous discharge of wheel fragments in the event of grinding wheel failure can be substantially eliminated by incorporating within the xed wheel guard a shutter assembly normally maintained retracted within the wheel guard and operative automatically in the event of grinding wheel failure to close the opening through which wheel fragments are discharged in the direction of the station normally occupied by the grinding machine operator.

The use of such a shutter within a wheel guard is contemplated in the Konrad patent referred to above, in U.S. Patent No. 1,158,127 of Geiger, in U.S. Patent No. 1,208,- 186 of Middleton, and U.S. Patent No. 1,447,996 of Muehlhauser. However, in each of these patents the shutter is mounted for rotation about a single axis either coincident with or close to the axis of rotation of the grinding Wheel, so that each of these shutters is best suited for use in association with a grinding wheel guard with a peripheral portion disposed substantially concentric of the grinding wheel, rather than for use with a grinding wheel guard of the configuration described in the copending application referred to above and also contemplated in this application.

Moreover, each of the shutter assemblies disclosed in the four patents referred to immediately above is evidently designed for incorporation in the grinding wheel guard for a relatively small offhand grinding machine where the workpiece being ground is normally held against the grinding wheel by hand, but such concentrically disposed shutter assemblies would be undesirable on a large grinding machine where they would strike a workpiece supported upon the grinding machine by opposing centers and perhaps knock it out of the machine, creating another hazard for the grinding machine operator normally stationed in front of the grinding Wheel close to the workpiece.

Summary In contrast to the fixed guards for large grinding wheels rotated at relatively high speeds which enclose most of the periphery and most of both sides of the grinding Wheel, already well known in the art, and in contrast to similar guards equipped with concentrically mounted rotatable shutters for smaller grinding wheels commonly mounted on oifhand grinding machines, already well known in the art, the instant invention provides a grinding Wheel guard composed of fixedly positioned interconnected portions arranged and particularly adapted for use in association with the hollow base of a grinding machine on which the grinding wheel enclosed by such a guard is rotatably mounted, which guard consists of spaced side portions and an interconnecting peripheral portion enclosing the half of the grinding Wheel most remote from the hollow base of the grinding machine and including as an accessory thereto a shutter assembly movable from a retracted position into a position closing the opening in the guard through which the grinding wheel and a workpiece to be ground are brought into engagement, Said shutter assembly being mounted for movement first downwardly and outwardly away from the grinding wheel then downwardly and inwardly toward the grinding wheel, and including a surface so disposed with the shutter assembly in its retracted position as to direct wheel fragments driven against it into the hollow base of the grinding machine by means of this surface and a lip at the lower edge of this surface extending toward lthe grinding wheel.

Noting that a grinding wheel is normally reduced substantially in diameter due to wear in use and to the truing operations necessary to maintain the grinding surface in proper condition, the instant invention also provides means for mounting the shutter assembly and for maintaining the shutter assembly normally in its retracted position supported entirely upon an adjustable hood so that the lip extending toward the grinding wheel from the shutter assembly may be positioned closely adjacent to the circumference of the grinding wheel as the diameter of the grinding wheel is reduced in use.

It is, therefore, an object of the present invention to provide a grinding wheel guard including as an element thereof a hood portion adjustable radially of a grinding wheel enclosed by the guard and supporting a shutter assembly therein in its retracted position.

Another object of the present invention is a grinding wheel guard provided with a shutter assembly mounted to rotate from its retracted position above a workpiece in engagement with the grinding wheel to a position be tween the workpiece and the grinding machine operator, when a grinding wheel enclosed by a grinding wheel guard so equipped breaks during a grinding operation.

Still another object of the invention is the provision of a grinding wheel guard incorporating a shutter assembly including both a portion enveloping part of the periphery of a grinding wheel and spaced side portions extending toward the center of the grinding wheel.

These objects are fully realized by the grinding wheel guard of the present invention.

Brief description of the drawing The invention will now be described in greater detail with reference to the drawing wherein:

FIG. 1 is a side view, partly in section of the upper front portion of the grinding wheel guard; and

FIG. 2 is a transverse vertical section thereof.

The improved grinding wheel guard as illustrated in the accompanying drawing comprises a stationary guard or housing 1 positioned over a grinding wheel 2 which during use wears down to a smaller diameter, as indicated at 2. A work table 3 rotatably supporting a workpiece 4 by suitable means such as a headstock and a foodstock, is positioned for engagement with the grinding wheel as shown in the drawing. The housing 1 carries a pivot pin 5 at its upper front edge as a pivotal support for an adjustable hood or visor 6 whose sides 6' have arcuate slots 7 along their lower edges for receiving clamping bolts 8 to hold the hood in adjusted position relative to the housing 1 and the grinding wheel 2 enclosed thereby. The surface of the hood 6 is arcuately curved to accommodate movement of the shutter supported thereby described further below, and the lower front edge of the hood 6 has an inwardly directed lip portion 9 for engagement with a coacting portion of the shutter.

Each of the sides 6 of the hood 6 has a pair of elongated links 10, 11 pivotally connected thereto at one end thereof, the links 10, 11 having their other ends pivotally connected to the respective sides or side `flanges 12 of a shutter 12 thus supported in its retracted position entirely by and within the hood 6. The shutter 12 also includes an upper lip portion extending transversely of its upper edge and away from the grinding wheel 2, and a 'lower lip portion 13 extending transversely of its lower edge and inwardly of the housing 1 substantially radially of the grinding wheel 2. The shutter 12 is immobilized in its retracted position by shear pins 14 interconnecting the respective side flanges 12 of the shutter 12 and the respective sides 6 of the hood 6.

Description of the preferred embodiment wheel is rotated at the proper operating speed to perform grinding operations on successive workpieces 4. As the grinding wheel 2 is reduced in diameter in use the hood 6 is periodically readjusted to maintain the lip portion 13 closely adjacent to the circumference of the grinding wheel.

In case of the accidental destruction of the grinding wheel while it is rotating within the grinding wheel guard embodying the instant invention, the broken fragments of the wheel move radially away from the center of the grinding wheel and clockwise as seen in FIG. 1 of the drawing. Broken fragments of the grinding wheel are received and contained in the upper portion of the housing 1 above the normal position of the grinding wheel 2 where the preferred embodiment of the housing has a free volume capable of receiving and containing a major portion of the volume of the grinding wheel. The flying fragments impinging upon the periphery of the housing 1 adjacent to the pivot 5 are directed against the upper rear portion of the shutter 12 with sufficient force to sever the shear pins 14, so that the shutter 12 is rotated rapidly about the pair of four bar linkages, each including links 10 and 11 pivotally connected to one side 6 of hood 6 and one side 12 of shutter 12, as indicated in FIG. 1. These linkages are so arranged that the shutter 12 is moved downwardly and outwardly of the grinding wheel guard into the opening through which the grinding wheel engages a workpiece so that the shutter 12 acts to trap the workpiece 4 in the grinding machine. This movement of the shutter 12 responsive to the force exerted by wheel fragments is limited by engagement of the lip portion 15 of the shutter 12 with lip portion 9 of the hood 6.

The mounting means for the shutter comprising a four bar linkage is particularly advantageous because it utilizes the energy contained in the wheel fragments to best advantage by moving the shutter in the same direction as the fragments, because it provides effective support for a relatively light weight shutter with relatively low inertia thereby capable of rapid movement through the substantial distance necessary to close the aperture through which the grinding wheel engages a workpiece, because the shutter so supported inherently rst moves outwardly and then inwardly as it moves downwardly to encompass both the grinding Wheel fragments and a workpiece disposed in engagement with the grinding wheel, and because the shutter is always maintained clear of the circumference of the grinding wheel thereby, even if it is released accidentally without failure of the grinding wheel.

The side anges 12' of the shutter 12 are extended inwardly of the grinding wheel guard a substantial distance beyond the pivotal connections with the links 10, 11 in order to increase their capability for trapping grinding wheel fragments which would otherwise be thrown out of the grinding wheel guard to either side of the shutter.

Finally, when the shutter of the instant invention is incorporated in a wheel guard of the configuration described in the copending application referred to above, it will be seen from the showing in FIG. 1 of the accompanying drawing that the shutter 12 in its initial fully retracted position provides an inner surface thereof properly angularly oriented to deflect grinding wheel fragments downwardly and rearwardly into the hollow base of the grinding machine and provides an inwardly extending lip portion 13 also effective for this same purpose during the short interval between fracture of the grinding wheel and the closing of the shutter 12.

-It will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions and, accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.

What is claimed is:

1. `In a grinding wheel guard comprising a relatively fixed section including rst and second spaced side portions disposed on opposite sides of a grinding wheel interconnected by a peripheral portion, and a relatively movable section including rst and second spaced side portions interconnected by a peripheral portion to form an adjustable hood, the improvement comprising (a) mounting means supported pivotally upon the adjustable hood;

(b) shutter means pivotally mounted upon said mounting means for movement from a retracted position within the adjustable hood to an extended position for trapping fragments of a broken grinding wheel;

(c) stop means for limiting displacement of said shutter means from its retracted positions; and

(d) shutter retaining means for maintaining said shutter in its retracted position.

2. A grinding wheeel guard as described in claim 1, wherein said mounting means comprises a pair of four bar linkages.

3. A grinding wheel guard as described in claim 2, -wherein said shutter means comprises a spaced pair of side portions extending toward the center of the grinding wheel guard interconnected by a peripheral portion.

4. A grinding wheel guard as described in claim 3, wherein said shutter retaining means comprises shear pins interconnecting said side portions of said shutter means and the side portions of the adjustable hood.

5. A grinding wheel guard as described in claim 3, wherein said stop means comprises a lip portion projecting outwardly from the upper end of said shutter means for engagement with a lip portion projecting inwardly from the lower end of the adjustable hood.

References Cited UNITED STATES PATENTS 1,351,908 9/1920 Howe 51--268 1,208,186 12/1916 Middleton 51-269 1,078,551 11/1913 Partridge 51--269 JAMES L. JONES, JR., Primary Examiner. 

